CN110072809B

CN110072809B - Apparatus and method for mass production of atomically thin two-dimensional materials including graphene

Info

Publication number: CN110072809B
Application number: CN201780063574.5A
Authority: CN
Inventors: 保罗·拉迪斯劳斯; 李·格拉斯哥; 罗兰·马歇尔
Original assignee: Thomas Swan and Co Ltd
Current assignee: Black Swan Graphene Inc
Priority date: 2016-10-13
Filing date: 2017-10-13
Publication date: 2022-08-19
Anticipated expiration: 2037-10-13
Also published as: WO2018069722A1; CN113636543A; ES2859149T3; US20210387203A1; CA3040229C; CN110087773B; CA3040228A1; WO2018069723A1; EP3526163A1; US20210237097A1; CN113636543B; CA3040229A1; CN110087773A; EP3525935A1; CA3113711A1; CA3040228C; US11565269B2; CN110072809A; US20190374954A1; EP3526163B1

Abstract

The present invention provides an apparatus for preparing graphene and similar atomic scale layered materials by layering bulk layered materials such as graphite; the device includes: a pump (112) for pumping a fluid at a pressure greater than 1MPa along a fluid conduit (12), the fluid being a suspension of solid particles of a bulk laminar material, the conduit and abutting; the impact head (16) has an impact surface perpendicular or substantially perpendicular to the trajectory of the incoming fluid so as to form a narrow and variable gap (20), the variation being regulated by direct or indirect pneumatic pressure. In use, the pressure exerted by the pumped fluid resists the force applied to the impact head along the main shaft. The device provides a layering device that unlocks automatically while maintaining high product quality and consistency. A relatively small change in gap size is sufficient to avoid clogging, such as occurs by the aggregation of large particles or groups of particles in the high shear gap used for stratification.

Description

Apparatus and method for mass production of atomically thin two-dimensional materials including graphene

The present invention relates to a method and apparatus for producing atomically thin two-dimensional materials (e.g., graphene). In particular, the present invention relates to a simple, scalable process for producing high quality, defect free, unoxidized two-dimensional materials, such as graphene, in commercially useful quantities. Such materials will have applications in composites, coatings, thermal management and electronic devices where properties of electrical conductivity, thermal conductivity, barrier and mechanical strength are important.

Background

Graphene is a two-dimensional allotrope of carbon, consisting of sheets of hexagonal structure of several atoms thick. Analogs of this material may include other chemicals including boron nitride and molybdenum disulfide.

Graphite, a widely used mineral, is actually a crystalline form of graphene in which graphene layers are bonded together by van der waals forces. Since 2004 as an isolating material was discovered, graphene has attracted considerable interest. The novel mechanical, thermal and electrical properties of the material suggest many uses. Graphene can be produced on a laboratory scale sufficient for experimental analysis, but commercial quantities are still a developing area of production. Other monolayer structures such as boron nitride are expected to exhibit similar interesting properties in the nanotechnology field.

Min Yi and Zhigan Shen write a review of this technology entitled "

review on mechanical evolution for the scalable production of graphene ", Journal of Materials Chemistry, A, 2015,3,11700 outlines the state of the art with respect to graphene production.

Bottom-up techniques, such as chemical vapor deposition and epitaxial growth, can produce high quality graphene with few defects. The resulting graphene is a good candidate for electronic devices. However, these thin film growth techniques have a limited scale and complex and therefore expensive production, and cannot meet the requirements for producing industrially relevant quantities of graphene.

The large-scale production of graphene at low cost has been demonstrated using top-down techniques, where graphene is produced by direct exfoliation of graphite, sometimes suspended in a liquid phase. The starting material for this is three-dimensional graphite, which is separated by mechanical and/or chemical methods to reveal graphene sheets several atoms thick.

The original technique used by graphene discoverers, the Scotch Tape method, can be used to prepare high quality and large area graphene sheets, which is extremely labor intensive and time consuming. It is limited to laboratory studies and seems infeasible to scale up industrial production.

The three-roll grinding technique is a method of expanding the scotch tape process, using polyvinyl chloride (PVC) dissolved in dioctyl phthalate (DOP) as the adhesive on the moving roll, which can provide continuous peeling. Although a three-roll mill is a known industrial technology, it is not easy and brings additional complexity to completely remove the residual PVC and DOP to obtain graphene.

High yields of graphene were developed by ultrasound assisted liquid phase graphite exfoliation in 2008 by the three colleges of Dublin (Trinity College Dublin). Starting from graphite powder dispersed in a specific organic solvent, followed by sonication and centrifugation, they obtained graphene dispersions. This method of producing graphene can be scaled up, but one disadvantage is that the resulting suspension has a very low graphene concentration (about 0.01mg/mL), which is not necessarily suitable for mass production.

In addition, the ultrasonic processor can only achieve the high power density required for small volumes, and it is therefore difficult to scale up the process to achieve any economies of scale. A related disclosure can be found in WO2013/010211A 1.

A shearing force technology.

It is well known that graphite layers have low resistance to shear forces, which makes graphite a useful lubricant. This has been exploited in a number of techniques which use shear forces to exfoliate graphene from graphite.

Ball milling is a common technique in the powder industry and is a method of generating shear forces. A secondary effect is the collision or vertical impact of the balls during the rolling action, which can break the graphene sheets into smaller sheets and sometimes even destroy the crystalline nature of the structure.

Several improvements to ball milling techniques have been attempted, such as wet ball milling with solvent addition, but these techniques still require very long processing times (about 30 hours) and produce a number of drawbacks even if suitable for industrial scale mass production. A related disclosure can be found in WO2012117251 a 1.

Some shear force generation techniques use an ion intercalation step before applying shear force to weaken interlayer bonding. This reduces the energy required to exfoliate graphite into graphene, but the resulting graphene can be contaminated with residual ions contaminating the finished product, and the process requires additional time and cost, which reduces the industrial application of the technology.

A fluid dynamics based approach has recently emerged for graphite exfoliation. These are based on mixing graphite in powder or flake form with a fluid to form a suspension, which can then be subjected to turbulent or viscous forces, which exert shear stress on the suspended particles. Typically, the fluid is a liquid of the type commonly used as a solvent, and it may include a surfactant mixture suitable for removing the solvent from the finished product.

One method of generating shear is to use high shear forces, such as a rotary mixer. Graphene exfoliation has been demonstrated using a kitchen blender to generate shear forces on graphite particles in suspension. The process has been scaled up using commercial high shear mixers, including rotating blades passing near a mesh screen to generate high shear. Due to the difference in velocity of the mixing blades and the static shear screen, the graphite particles are subjected to shear forces exerted by the fluid. Relevant disclosures may be found in WO2012/028724a1 and WO2014/140324a 1.

Another method is to use a high pressure homogenizer with a microfluidizer. In this case, the microfluidizer consists of channels having microscale dimensions, meaning about 75 μm. High pressure is used to force fluid from the inlet to the channel. This technique is derived from the treatment of fluids for the production of milk, as disclosed for example in EP 0034675, US8585277B2 and WO2016174528a1, but this device is not suitable for use with suspended solids, since this would lead to blockages and high wear rates, since milk production plants for the homogenization of fluids are a different technical problem in terms of engineering. Due to the narrow dimensions of the channels, viscous friction between the walls and the bulk flow generates high shear forces, which results in graphite delamination. This process requires very high pressures and the starting graphite must have been crushed to the micron size range. A related disclosure can be found in WO 2015/099457.

Further variations can be found in Nacken, SC Advances, 2015,5, 57328. Here, the fluid is discharged through the nozzle into the void against the valve, creating a back pressure to avoid cavitation in the expansion chamber. Here, a material such as graphene delaminates as the fluid exits the nozzle into the expansion chamber.

There is a need for a graphene production process that can produce graphene using less energy, which can be scaled up to high production rates without loss of quality of the final product. Such devices are disclosed in co-pending patent applications GB15181.5 and PCT/GB 2016/053177. The apparatus provides a fluid conduit for impacting a particle suspension to be delaminated against an impact head having an impact surface and an annular gap. In practice it has been found that the device has a limited lifetime before maintenance is required, since the annular gap may become clogged with particulate material and/or worn, providing an uneven gap through which the suspension preferentially flows and which in turn makes the gap larger. While these two problems tend to be mutually exclusive, this is not necessarily so. Clogging tends to occur when new suspension is introduced, i.e. larger particles and unworn head. This type of wear tends to occur after prolonged use and can create paths of least resistance through which larger particles can escape but with poor stratification. If the purpose of the apparatus is for industrial scale delamination of a layered material suspension, e.g. for the production of graphene from graphite, and the industrial production requires long operation times (e.g. several days or more hours of operation), it would be desirable to provide an improved apparatus. This application mainly addresses the problem of plugging.

Definition of the invention

The present invention seeks to overcome the problems of the prior art to provide a graphene apparatus and production method that is fast, scalable to industrial quantities and energy efficient.

Various aspects of the invention are as set out in the appended claims.

In a first aspect, the present invention provides:

an apparatus for producing graphene and similar atomic scale layered materials by delaminating a bulk layered material, such as graphite; the apparatus comprises a main pump (112) and a core member (10),

the main pump (112) being adapted to pump fluid at a pressure greater than IMPa, in a first direction and along the main axis towards and in fluid communication with the core member, the fluid being a suspension of solid particles of bulk laminar material;

the core component (10) comprising a fluid conduit (12), an impact head (16) and an impact head surround (26),

said fluid conduit (12) defining a main axis along which fluid is pumpable and adapted to convey said fluid, wherein the fluid conduit is arranged to direct fluid under said pressure from the conduit against said impact head (16);

the impact head (16) has an impact surface (28) perpendicular or substantially perpendicular to the main axis, thereby generating a resultant force in the first direction; the impact head and the conduit are arranged such that a variable, preferably annular gap (20) of between 500 μm and 1 μm is formed between an end (24) of the conduit proximate the impact head and the impact head, wherein the gap forms a continuous region around the conduit end and substantially coplanar with the impact head;

the impact head surround (26) extends the confined area before fluid exits the core component,

wherein the device is configured to bias the impact head in a second direction, directly opposite the fluid in the first direction, and with a second force; and

an impact head (16) of the apparatus is configured to be movable along the main shaft relative to a proximal end (24) of the conduit so as to vary the gap (20), and the movement is a result of a magnitude of a first force that opposes, directly or indirectly, a second force that is a result of pneumatic pressure that opposes the first force applied to the impact head along the main shaft.

In summary, in use, the impact head movement is dependent on a balance of the forces exerted by the pumped fluid and the reaction forces exerted from the pneumatic pressure, such that as the back pressure of the pumped fluid increases, for example due to a blockage of the gap the pneumatic pressure increases, the pneumatic volume decreases and the impact head moves along the main shaft to increase the gap size and clear the blockage. Thereafter, the pressure on the pumped fluid from the device is reduced and the gap is restored to the desired position. A stop may be provided to limit the movement of the impact head along the main shaft. The first end stop may be used to maintain a minimum clearance regardless of pneumatic pressure (e.g., when fluid pumping has not yet begun). The second end stop may be used to provide maximum clearance regardless of fluid pressure (e.g., when the clearance becomes blocked).

Thus, in use, fluid ahead of the impact head exerts a back pressure on the upstream main pump work, and the impact head (16) of the device is configured to be movable along the main shaft relative to the conduit proximal end (24), which results in a change in the annular gap (20), the change being regulated by pneumatic pressure, for example by a pneumatic linkage from the control device. The pneumatic pressure is opposite to the back pressure such that the gap varies with the back pressure in use. The variation need not be large and a variation of about 1 to 100 μm, preferably 2 to 10 μm, may be sufficient to provide the benefit of reducing the occlusion/occlusion gap.

The device solves the problem of blockage. In particular, it has been found in use that blockage of the gap between the impact head and the end of the pipe results in an increase in back pressure, while this in itself can be expected to clear any blockage, which is not the case in practice. Some blockages appear to be associated with particles that cannot pass through the 500 μm to 1 μm gap, but practice has shown that other mechanisms may work. In any case, devices with fixed clearances can become clogged or at least the back pressure increases over time, increasing wear of the pump and requiring higher energy requirements for the device in use.

Preferably, the impact head is symmetrical about a longitudinal axis aligned with a main axis adapted to convey said fluid, such that the symmetry allows the head to rotate. Suitable symmetries will include that the impact head is cylindrical and/or (frusto-) conical or consists of cylindrical and/or (frusto-) conical sections. The symmetry is preferably radial symmetry about the main axis. This is because asymmetric devices such as shown in WO2015/099378 provide less uniform product layering. This is believed to be because there are various ways of passing through high shear fields. Also, the low turbulence areas collect solid deposits from the fluid, which can lead to clogging and plugging. This occurs gradually, especially when the flow rate is changed (e.g., at start-up), the deposit cake can move and clog the flow path and require equipment stripping and cleaning.

In a second aspect, the invention therefore also includes the use of the apparatus described herein for the preparation of graphene and similar atomic scale layered materials by delamination of bulk layered materials. The layered material is preferably selected from graphite, hexagonal boron nitride or molybdenum disulphide. A reduction in clogging can be observed using the devices described herein.

This arrangement solves the problem of clogging because the increased back pressure, i.e. the fluid pressure at the impact head, compresses the gas in the pneumatic linkage, which then causes the gap size to increase, thereby releasing the material trapped in the gap. In practice, the process appears to be more complex than this, since the degree of movement appears to be very small, and it is speculated that an additional mechanism appears to be that small fluctuations in the normal fluid supply pressure cause a slight pumping action of the impact head, acting as a reciprocating crusher to trap particles, so that no significant blockage occurs requiring a significant increase in back pressure. In other words, even a small amount of pneumatic adjustment movement is sufficient to avoid clogging, for example from 1 to 10 μm. This has the following advantages: the system does not periodically expel large amounts of material that do not pass through the normal gap size and surprisingly maintains quality even if the gap size is not constant.

From the above it can be understood how the variation is regulated by means of pneumatic pressure, for example by a pneumatic linkage, as a function of the back pressure. The linkage is described as being pressure regulated, which means that the pneumatic linkage is directly responsive to back pressure, which causes the impact head to move along its axis, but may be implemented by means such as an intermediate mechanical function, e.g. a lever. Similarly, the pneumatic linkage need not be, and preferably is not, a simple air pocket behind the impact head, as the pressure makes direct pneumatic compression potentially unreliable. Therefore, it is preferred that a pneumatic element such as an air bag acts on the intermediate mechanical linkage such that the pneumatic pressure is preferably less than the back pressure, and it is highly preferred that the back pressure and the pneumatic pressure of the incoming fluid in use are in the range of 10: 2 to 10: between 0.1. This serves to achieve a ready regulation of the pneumatic pressure, for example by incoming compressed air or by a release valve. The present arrangement has the additional advantage that not only is the gap variable at a given setting (i.e. the gap will vary around an average), for example at a given volume of pneumatic gas, but the total amount of gas can be varied so that the overall average gap is easily varied at any given time. (i.e., the gap will vary around a different, higher or lower average value, for example if gas is withdrawn or added, respectively).

The term back pressure refers to the pressure of a suspension of suspended layered material to be stratified in use as it is applied against the impact face of the impact head.

The pneumatic pressure of the gas may be that of air or, preferably, an inert gas such as nitrogen, preferably dry nitrogen.

The apparatus of the present invention results in a more reliable and easily adjustable apparatus for suspending the layering of layered materials, such as graphite, hexagonal boron nitride and molybdenum disulfide, for industrial production of their respective layered materials.

Preferably, the device used in the present invention is graphite, hexagonal boron nitride or molybdenum disulphide particles as solid particles. Most preferably, the solid particles are graphite.

The fluid may be a suspension with a particle size in the range of 1 μm to 1000 μm. The advantages and capabilities of this general type of device have been disclosed in co-pending uk patent application GB 15181.5. It has been found that the device is capable of delaminating graphite and similar layered materials at pressures and energy levels lower than those required for microfluidizers. This has the additional advantage of reducing heat build-up in the process.

The annular gap is very advantageous for providing a consistent product, arranged (substantially) vertically and within the narrow band of the pneumatic adjustment movement. Thus, substantially perpendicular includes at most a 10 ° offset, preferably no more than 1 °, and most preferably no more than 0.1 °. This offset may be conical.

However, consistent product quality may not be achieved after prolonged use, sometimes not exceeding several hours. As can be seen from the exaggerated example in fig. 6, weak points in the impact head can cause local erosion and the annular gap can become non-uniform, creating a larger sized local channel, which can wear down to that shown in fig. 1, during which the product quality rapidly degrades as the amount of suspension that undergoes the required shear/impact conditions of the equipment decreases and the pressure drop over the impact head also decreases.

It has been found that providing an impact head that is symmetrical about a longitudinal axis and coincident with the main shaft overcomes the problem of selective wear. It appears that having a symmetrical head allows a certain degree of rotation, which is used for even wear. This is surprising because in the initial view the rotatable head should rotate to give the maximum aperture size in order to relieve the incoming pressure and therefore local wear should be exacerbated. However, while not wishing to be bound by theory, it is speculated that the high turbulence in the device generates non-linear forces and may be combined with vibrations. This means that the force causing the head to rotate may exceed the force that preferentially orients it to provide maximum clearance.

The effect of this rotational capability due to the symmetry of the impact head with respect to the incoming fluid can be seen by operating the replacement head for a similar length of time, as shown in fig. 7. Some evidence suggests local wear in the range of about 50 deg., as indicated by the lighter color, but this is by no means the extent shown in fig. 1, where local wear is understood to widen rapidly to provide the notch shown.

The impact head of the device can rotate freely around the main shaft. As mentioned above, this has proven to be effective.

The impact surface of the impact head may be symmetrical. This is preferred, for example to cause the impact head to rotate and thus be more prone to even wear, since asymmetry has not been found to be beneficial, in practice local wear does occur (e.g. if there is a notch) or, if configured to cause rotation, the high pressure of the device creates such a degree of rotation that rotation, chatter and wear of the orifice in which the impact head is located may occur.

However, it is also envisaged that the impact head (16) of the device is configured to be rotatable about the main shaft and constrained by the mechanism. The mechanism may for example be a shaft with a drive rate, for example 0.1 to 10 revolutions per minute. But this is not preferred as it creates additional complexity and may be difficult to implement in view of the forces and pressures involved.

For the sake of completeness, the impact head of the device of the invention is rotatable. The term will be interpreted by the skilled person to mean that rotation may occur under the action of operating forces. This does not mean that the head must be free to rotate or be able to move by hand or even with a simple tool, for example when not in operation, as the clearance of the components is tight, for example an impact head received in a bore of the apparatus.

Accordingly, the present invention includes an apparatus having an impact head of the aforementioned geometry and a pneumatically-adjusted adjustment mechanism, as described herein.

The impact head may comprise a common engineered material, such as steel. This is not surprising since the prior art discloses that all use steel or stainless steel equipment, considering that graphite and graphene are good lubricants. In particular, the graphite has a hardness (Mohs hardness) of 1 to 2 and a hardness (Vickers hardness) of VHN 10-7 to 11kg/mm ² In contrast, conventional 4-4.5 hardness (mohs hardness) steels compared to high speed steels, VHN10 ═ 7-11kg/mm ² . However, we have surprisingly found that harder impact head materials provide greater throughput. While not wishing to be bound by theory, it is believed that for harder materials, the impact head is less elastic and therefore peels more effectively. However, chromium, which has a hardness (mohs hardness) of 8.5, is not necessarily better than steel (wear and abrasion with high quality graphite is not a problem), while alumina, silicon nitride, tungsten carbide, silicon carbide, boron nitride and diamond are preferred. In particular, diamond is most preferred. While not wishing to be bound by theory, it appears that the energy of interaction between diamond and graphite (both carbon materials) is minimal, but the crystals of diamond and graphiteThe difference in structure creates the necessary stiffness.

It has been found that the apparatus of the present invention is more effective when the impingement head is cooled. It is not entirely clear why this occurs because the viscosity of the fluid should be greater at low temperatures. The apparatus of the invention preferably comprises a cooled impact head, the apparatus preferably being configured such that the impact head can be maintained at a temperature below 50 ℃ in use at a flow rate of greater than 1000 litres per hour. Preferably less than 25 deg.c and most preferably less than 10 deg.c. It has been found that the most effective surface cooling of the impact head can be obtained using a diamond impact head.

Method of the invention

In a third aspect, the present invention provides a method of exfoliating a laminar material to produce an atomically laminar material by delamination of a bulk material; the method comprises the following steps: the apparatus described above is provided and the layered material is suspended in the liquid.

In the method of the present invention, the layered material is preferably graphite, and the atomic-scale layered material is graphene.

The liquid in which the layered material is suspended is preferably water. Water is preferred because it has a high specific heat capacity, which enables the process to be operated at temperatures in the range of 30 ℃ to 80 ℃. In addition, the aforementioned local head temperature is preferably lower than room temperature, which is easier to maintain with water as the liquid. Other suitable liquids are liquid hydrocarbons.

The process of the invention is preferably operated at a temperature of from 30 ℃ to 80 ℃.

The particle size range of the graphite is preferably from 1 μm to 1000 μm, more preferably from 3 to 50 μm, most preferably from 15 to 25 μm. The dimensions may be determined using a Malvern Mastersizer using D4,3 particle size measurement.

The layered material, preferably graphite, loaded in the liquid phase is preferably in the range of up to 500 grams per liter (g/l). More preferably, the layered material loading is from 10 to 125g/l, most preferably 125 g/l.

The fluid of the invention impacts the impact head at a pressure greater than IMPa, more preferably at a pressure of from 10MPa to 150MPa, more preferably at a pressure of from 40MPa to 100MPa, most preferably at a pressure in the range of from 50MPa to 70 MPa. Pressure selection can provide optimum yield, productivity and energy consumption. Thus, the pneumatic counter pressure against the back pressure is preferably regulated by a pneumatic linkage as a function of the back pressure to avoid the need for a very high pressure air seal, which may hinder the variation of the movement of the impact head.

It has surprisingly been found that instead of simply having a higher pressure the better, which may result in a higher impact force on the impact head, an optimal pressure range is found. This optimal range provides the highest quality laminate, such as graphene. While not wishing to be bound by theory, it is believed that excessive system energy causes the laminate to rupture. Thus, there is an optimum pressure range for a system configured with an impact head so that solids in the fluid are laminated (peeled off) while the peeled laminar sheet is not excessively damaged.

The process of the present invention preferably comprises a fluid in which the surfactant is present. Suitable surfactants include sodium alkyl benzene sulphonate and tetrabutylammonium chloride. The preferred surfactant is sodium cholate.

The surfactant is preferably an anionic or cationic surfactant which can be neutralised to remove its anionic or cationic character respectively, so that the surfactant can be easily removed from the fluid. Thus, the process of the invention optionally comprises the following neutralization step: the fluid resulting from the process is taken, which comprises an anionic or cationic surfactant and a sheet of a layered material, preferably graphene, and the surfactant is neutralized before washing the surfactant from the sheet (which may precipitate in the process) to produce a composition consisting of the sheet of the layered material.

The process of the invention preferably comprises a filtration step, wherein particulate material is removed by said filtration step (using any mechanism). The filtration step may preferably be performed after the neutralization step.

The invention also includes a second aspect of the use of a high pressure homogenizer, for example of the type disclosed with reference to the drawings, for the preparation of graphene from graphite in aqueous suspension.

The conditions and parameters associated with the method of the invention are also applicable to the configuration of the apparatus of the invention. Unless otherwise stated, the temperature is 25 ℃ and the atmospheric pressure is 1 atm.

DETAILED DESCRIPTIONS

The apparatus of the present invention will now be described by way of the following figures, in which:

FIG. 1 shows a schematic view of the fluid path through the device of the present invention and shows the core member;

figure 2 shows a schematic cross-sectional view of a first arrangement of core parts of the inventive device;

figure 3 shows a schematic cross-sectional view of a second arrangement of core parts of the inventive device;

figure 4 shows a schematic cross-sectional view of a second arrangement of core components of the inventive device;

fig. 5 shows a schematic view of the system or apparatus of the invention comprising a core component and an auxiliary component to provide an optimal handling system for performing the method of the invention.

Fig. 6 shows an impact head that is damaged and rotationally constrained during prolonged use.

Fig. 7 shows an impact head that suffers minimal wear and is not rotationally constrained over extended use.

The chart provides the following features:

10 assembly of core parts;

12 fluid conduits/volumes;

14 into the fluid conduit at a point remote from the impact head;

16 a percussion head assembly;

18 an optional face (impact face) of the impact head assembly;

20 rings/ring gaps;

202 frustoconical ring/frustoconical annular gap;

204 outer ring/outer ring gap;

22 support structure:

24 an outlet of the fluid conduit proximate the impact head/conduit proximal end;

242 proximal end of tubing, alternative forms;

26 impact head surround;

28 impact the head face;

32 pipes/tubes; (FIG. 5 below).

100 systems or (expansion) devices of the invention;

110 a raw material container;

112 a high pressure pump;

114 a valve;

124 a pressure reducing valve;

116 a finished container;

118 water chiller/cooler.

Referring to figures 1 to 4, in use, the apparatus of the present invention has fluid pumped from a pump 112 through

conduits

32 and 12 in the form of tubes, the

conduits

32 and 12 being end portions of the core assembly 10. Core assembly 10 has proximal end 24 of tube 12/32, wherein fluid in the volume of pipe 12 exits the pipe under pressure to impact head 16, which impact head 16 may have a hard material face 18; as the fluid strikes the surface of the impact head, it passes through the annular space 20 defined between the surface 28 of the impact head and the proximal end of the conduit 24, and then exits the core components, for example, for recirculation or recovery as a finished product. In the particular figure, a further impact head surround 26 is provided to extend the region of fluid confinement prior to exiting the core components in use. The impact head 16 of the device is configured to be movable relative to the proximal end of the conduit 24, thereby defining the annular gap 20.

As indicated by the arrow in fig. 1, the impact head 16 may be moved towards the proximal end of the conduit 24 by a mechanism such as a screw adjustment to effect a general change in position of the impact head and thereby create a gap, the operation being maintained in the range between 500 μm and 1 μm. The device of the invention provides pneumatic pressure in the same direction as the arrow, however, the movement of the head is limited in order to maintain a minimum clearance, for example by using end stops. In use of the device, as shown in FIG. 2, the impact head 16 with the optional impact surface 18 is able to adjust its position, as indicated by the double-headed arrow. In use, this regulation is controlled by the pressure exerted by the incoming suspension of stratified bulk material at the inlet of the fluid conduit at a point 14 remote from the impact head (referred to as back pressure), as opposed to the pressure exerted from pneumatic pressure. Thus, as the back pressure increases, the impact head will move away from the proximal end of the conduit 24 so as to increase the annular gap 20 and thus clear any blockage. Similarly, once the blockage has cleared, the pressure will drop for a given incoming liquid, as the obstruction to liquid flow through the device is reduced and the impact head will move again, which will reduce the gap. The maximum retraction of the impact head due to back pressure may be limited by the end stop and, as mentioned above, the maximum advancement of the impact head will also be limited by the end stop. By means of the above-described mechanism, the permissible variation of the movement of the impact head, for example regulated by a pneumatic linkage, is preferably in the range of 1 to 100 μm, so that blockages are cleared, 1 to 10 μm being sufficient in many cases to prevent the build-up of blockages.

In figure 3 the proximal end of conduit 242 has an internal bevel such that in use fluid passing from the volume of conduit 12 through the core member is accelerated in the annular space (now frusto-conical) until the pinch point is reached, creating maximum shear.

In fig. 4, the proximal end of the conduit 24 does not abut the impact head barrier and provides an outer annular region 204 in which turbulent flow can occur to improve processing. Outer annular region 204 is presented in fig. 3 with an inner inclined surface, fig. 3 may be provided without region 204.

With reference to fig. 5, the handling system of the invention comprises a core part 10 as described before. The system is configured such that the feedstock is provided in a vessel 110 and pumped by a high pressure pump 112 into a conduit 12/32, into the core components 10, in particular the impact head 16, and then out to an optional pressure drop valve 124, providing back pressure to the core components to improve processing. The system is further configured such that the fluid then passes as a finished product through the directional control valve 114 to the product container 116, or through recirculation through a cooler 118 into the high pressure pump 112 for optional recirculation.

Experiment of

The apparatus of the present invention comprises a 3kW impeller pre-pump at 400kPa output, a 30kW multi-piston main pump, a graphite suspension having an average particle size of 20 μm and 100g/l of graphite solid particlesPellet, pressure 60MPa (+/-1MPa), flow rate 1200 litres per hour along a fluid conduit having a main axis, cylindrical impact head having an end impact face perpendicular to said main axis. The cylinder is 15mm in diameter and 25mm in length and is disposed in a corresponding bore of the housing (itself a 20cm long cylinder) which receives a 10 to 15mm cylindrical impact head (from a first end stop to a second end stop). The gap is set to 5 μm in the fully extended first end stop position. The suspension was initially at a temperature of 20c, maintained at a temperature of 30 c by cooling and then recycled back to the apparatus. The recirculation loop has a hold up of 500 litres. The base of the cylindrical impact head (the face away from the impact face) is supported by the housing and is biased outwardly (by pneumatic force) at a first end stop. The biasing force is set to be more than 10% above the biasing force from operation in the first direction of pumping fluid (i.e. in use). The impact head is located in the housing with a clearance fit according to ISO 286-2H 7. The machine was run for 15 minutes. The foregoing are test 1 and test 4. the experiments were repeated with fresh suspension and the impact head was mechanically fixed to a first end stop with a 5 μm gap. These are run 2 and run 3. The pneumatic pressure (second pressure generating the second force) is not applied directly to the impact head, but through a mechanical linkage, generating about 100: 1, from about 25: 1 (exceed pi due to the fluid 15/2) ² mm ² ) And the mechanical leverage of the remainder.

As a result:

it is believed that head movement serves to prevent clogging by breaking and removing material before significant back pressure is created. Clogging was also indirectly evidenced by the visual residue on the equipment upon disassembly. While plugging can be avoided by using finer starting materials, this requires a pretreatment run to reduce the feedstock size and convert the continuous process to a less efficient batch process. Since the apparatus will operate with two gap sizes, larger gaps can also be used, which will result in longer processing times. The degree of influence of the head movement is deduced from the pressure change. The products of runs 1 and 4 included graphene. The fluctuations indicate an oscillation of the impact head, which is a sequence of the pumping frequency of the main pump pistons. This indicates the synergy of the piston pump and the head movement. There is no reason to believe that the present invention is not applicable to an unmodulated fluid supply, but modulation indicates a synergistic effect of these two characteristics.

The present invention provides a device that is more resistant to plugging when used with suspended solids that can delaminate.

The mechanical advantage is the ratio of the force generated by the machine to the force exerted on it, used to evaluate the performance of the machine. The preferred mechanical advantage is 50: 1 to 200: 1, since this allows the use of conventional pneumatic pressure equipment, for example an overpressure of about 0.5 Mpa. The pressure here is a pressure above atmospheric pressure. Unless otherwise stated, the temperature herein is 20 ℃.

The preferred embodiment of the invention is:

an apparatus for producing graphene and similar atomically layered materials from layered bulk layered materials (e.g. graphite); the apparatus comprises a main pump (112) and a core member (10),

the main pump (112) being adapted to pump fluid at a pressure greater than IMPa towards and in fluid communication with the core member (10), the fluid being a suspension of solid particles of a bulk laminar material;

the component (10) comprises a fluid conduit (12), an impact head (16) and an impact head surround (26):

a fluid conduit (12) having a main shaft adapted to convey the fluid, wherein the fluid conduit is arranged to direct fluid under pressure from the conduit against an impact head (16);

the impact head (16) has an impact surface perpendicular or substantially perpendicular to the main axis; the impact head and the conduit are arranged such that a variable, preferably annular, gap (20) of between 500 μm and 1 μm is created between the end of the conduit near the impact head and the impact head, wherein the gap forms a continuous region around the conduit end and substantially coplanar with the impact head; and

an impact head surround (26) extends the confined region of the fluid prior to exiting the core component, wherein,

the impact head (16) of the device is configured to be movable along the main axis relative to the proximal end of the conduit (24) so as to cause the gap (20) to vary, and wherein

This variation is regulated, directly or indirectly, by the pneumatic pressure which opposes the force applied to the impact head along the main shaft, which is generated by the pressure exerted, in use, by the pumped fluid.

2. The apparatus of embodiment 1 further comprising a pressure drop valve (124) downstream of the impact head so as to maintain a second back pressure behind the impact head in use.

3. The apparatus of embodiment 1 wherein the arrangement between the impact head face and the main axis is 1 ° or less from vertical.

4. The device according to any preceding embodiment, wherein the impact head (16) of the device is freely rotatable about the main shaft.

5. The device according to any of embodiments 1 to 4, wherein the impact head (16) of the device is configured to be rotatable about a main axis and constrained by a mechanism.

6. The apparatus according to any preceding embodiment wherein the proximal end of the conduit (242) has an internal inclined surface such that the annular gap is frusto-conical, whereby in use fluid is transferred from the volume of the conduit (12) through the core member, accelerating until a minimum width of the annular gap is reached to generate maximum shear forces.

7. The apparatus of embodiment 6, wherein the annular gap has a width between 500 μm and 200 μm at its widest point and between 200 μm and 1 μm at its narrowest point.

8. The apparatus according to any preceding embodiment, wherein the proximal end of the conduit (24) does not abut the impact head surround and provides an outer annular region (204).

9. The apparatus of any preceding embodiment, further comprising a cooler (118) in fluid communication with the fluid conduit and the main pump, such that suspension to be treated will pass through the cooler and out to the main pump before passing through the core components (10), the cooler being configured to reduce the temperature of the fluid.

10. The apparatus of claim 9, further comprising a second low pressure pump in fluid communication with an inlet of the cooler, an outlet of the cooler being in fluid communication with the main pump such that the suspension is first drawn into the second pump, through the cooler and out to the main pump, and then through the core components (10).

11. The apparatus according to any preceding embodiment, wherein the impact face (18) of the impact head (16) comprises a material selected from tungsten carbide, zirconia, silicon nitride, alumina, silicon carbide, boron nitride and diamond.

12. The apparatus according to any preceding embodiment, wherein the impact face (18) of the impact head (16) comprises diamond.

13. A method of exfoliating a laminar material to produce an atomically laminar material by layering of a bulk material; the method comprises the following steps: providing the apparatus described in example 1; the layered material is suspended in the device in a liquid at a pressure greater than IMPa.

14. The apparatus or method according to any preceding embodiment, wherein fluid exiting the core components is recirculated back to the inlet of the main pump, optionally via the cooler of embodiment 9 and/or the second pump of embodiment 10.

15. The apparatus or method according to any preceding embodiment, wherein the temperature of the fluid is maintained in the range of 30 ℃ to 80 ℃

16. The method or apparatus of any preceding embodiment, wherein the fluid impinges on the impingement head at a pressure of 10MPa to 150 MPa.

17. The method or apparatus of any preceding embodiment, wherein the fluid impinges on the impingement head at a pressure of 50MPa to 70 MPa.

18. A method or apparatus according to any preceding embodiment, wherein the fluid impinges on the impact head at a flow rate of more than 1000 litres/hour.

19. The method or apparatus according to any preceding embodiment, wherein the particles range in size from 3 μm to 50 μm.

20. The method or apparatus according to any preceding embodiment, wherein the layered material is loaded in the liquid phase in a range up to 500 grams per liter (g/l).

21. Use of the apparatus of any one of embodiments 1 to 12 for the preparation of graphene and similar atomic scale layered materials by delamination of bulk layered materials.

22. Use of the apparatus of any one of embodiments 1 to 12 for the preparation of graphene and similar atomically layered materials, wherein the solid particles are particles of graphite, hexagonal boron nitride or molybdenum disulphide.

23. Use of the apparatus of any one of embodiments 1 to 12 for the preparation of graphene from an aqueous graphite suspension.

Claims

1. An apparatus for producing graphene and similar atomic scale layered materials by layering of bulk layered materials; the apparatus comprises a main pump (112) and a core member (10):

the main pump (112) being adapted to pump fluid, which is a suspension of solid particles of a bulk laminar material, in a first direction and along a main axis towards the core parts (10) and in fluid communication with the core parts (10) at a pressure of more than 1 MPa;

the core component (10) comprising a fluid conduit (12), an impact head (16) and an impact head surround (26);

said fluid conduit (12) defining a main axis along which fluid can be pumped and being adapted to convey said fluid, wherein the fluid conduit is arranged to direct fluid under said pressure from the conduit against said impact head (16);

the impact head (16) having an impact surface (28) perpendicular or substantially perpendicular to the main axis, thereby generating a resultant first force in the first direction; the impact head and the conduit are arranged such that a variable gap (20) of between 500 μm and 1 μm is formed between the end of the conduit proximate the impact head and the impact head, wherein the gap is formed as a continuous region around the conduit end and substantially coplanar with the impact head; and

the impact head surround (26) allows for an extension of a region of fluid confinement prior to exiting the core component, wherein,

the device is configured to bias the impact head in a second direction directly opposite the fluid of the first direction and with a second force, an

An impact head (16) of the device is configured to be movable along a main axis relative to the proximal end of the conduit so as to cause the gap (20) to vary, and

the movement is a result of the magnitude of a first force opposing a second force, the second force being a result of pneumatic pressure directly or indirectly opposing the first force applied to the impact head along the main shaft.

2. The apparatus of claim 1 further comprising a pressure drop valve (124) downstream of the impact head so as to maintain a second back pressure after the impact head in use.

3. The device according to any of the preceding claims 1-2, wherein the impact head (16) of the device is freely rotatable around the main shaft.

4. The device according to any of the preceding claims 1-2, characterized in that the impact head (16) of the device is configured to be rotatable about a main axis and is mechanically constrained.

5. The arrangement according to any of the preceding claims 1-2, further comprising a cooler (118) in fluid communication with the fluid conduit and the main pump, such that the suspension to be treated will pass through the cooler and out to the main pump and then through the core components (10), the cooler being configured to reduce the temperature of the fluid.

6. The apparatus of claim 5, further comprising a second low pressure pump in fluid communication with the inlet of the cooler and the outlet of the cooler is in fluid communication with the main pump such that the suspension is first drawn into the second pump, through the cooler and out to the main pump and then through the core components (10).

7. The apparatus of any of the preceding claims 1-2, wherein the main pump has a reciprocating motion configured to cause pressure fluctuations in the fluid and thus fluctuations in the magnitude of the first force.

8. The device of any of the preceding claims 1-2, wherein the pneumatic pressure is indirectly opposed to the first force and the second force is applied to the impact head through a mechanical linkage, thereby providing a mechanical advantage.

9. Device according to the preceding claim 1, wherein the gap (20) is annular.

10. The device according to any of the preceding claims 1-2, wherein the layered material loaded in the liquid phase is in the range of up to 500 grams per liter (g/l).

11. A method of exfoliating a laminar material to produce an atomically laminar material by stratification of a bulk material; the method comprises the following steps: providing the device of claim 1; passing a liquid suspension of the layered material through the apparatus at a pressure greater than 1 MPa.

12. The method of claim 11 wherein fluid exiting the core components is recirculated back to the inlet of the main pump.

13. The method of claim 12 wherein fluid exiting the core components is recirculated back to the inlet of the main pump via the cooler of claim 5 and/or the second pump of claim 6.

14. The method of any one of claims 11-13, wherein the temperature of the fluid is maintained in the range of 30 ℃ to 80 ℃.

15. The method of any one of claims 11-13, wherein the particles range in size from 3 μ ι η to 50 μ ι η.

16. The method of any of the preceding claims 11-13, wherein the layered material loaded in the liquid phase is in a range of up to 500 grams per liter (g/l).

17. Use of the device of any one of claims 1 to 6 for the preparation of graphene and similar atomically layered materials by delamination of bulk layered materials.

18. Use of the device according to any one of claims 1 to 6 for the preparation of graphene and similar atomically layered materials, wherein the solid particles are graphite, hexagonal boron nitride or molybdenum disulphide particles.